//请你判断一个 9 x 9 的数独是否有效。只需要 根据以下规则 ，验证已经填入的数字是否有效即可。 
//
// 
// 数字 1-9 在每一行只能出现一次。 
// 数字 1-9 在每一列只能出现一次。 
// 数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。（请参考示例图） 
// 
//
// 
//
// 注意： 
//
// 
// 一个有效的数独（部分已被填充）不一定是可解的。 
// 只需要根据以上规则，验证已经填入的数字是否有效即可。 
// 空白格用 '.' 表示。 
// 
//
// 
//
// 示例 1： 
// 
// 
//输入：board = 
//[["5","3",".",".","7",".",".",".","."]
//,["6",".",".","1","9","5",".",".","."]
//,[".","9","8",".",".",".",".","6","."]
//,["8",".",".",".","6",".",".",".","3"]
//,["4",".",".","8",".","3",".",".","1"]
//,["7",".",".",".","2",".",".",".","6"]
//,[".","6",".",".",".",".","2","8","."]
//,[".",".",".","4","1","9",".",".","5"]
//,[".",".",".",".","8",".",".","7","9"]]
//输出：true
// 
//
// 示例 2： 
//
// 
//输入：board = 
//[["8","3",".",".","7",".",".",".","."]
//,["6",".",".","1","9","5",".",".","."]
//,[".","9","8",".",".",".",".","6","."]
//,["8",".",".",".","6",".",".",".","3"]
//,["4",".",".","8",".","3",".",".","1"]
//,["7",".",".",".","2",".",".",".","6"]
//,[".","6",".",".",".",".","2","8","."]
//,[".",".",".","4","1","9",".",".","5"]
//,[".",".",".",".","8",".",".","7","9"]]
//输出：false
//解释：除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。 但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无
//效的。 
//
// 
//
// 提示： 
//
// 
// board.length == 9 
// board[i].length == 9 
// board[i][j] 是一位数字（1-9）或者 '.' 
// 
//
// Related Topics 数组 哈希表 矩阵 👍 1189 👎 0

package leetcode.editor.cn;
//java:有效的数独
public class Q0036ValidSudoku {
    public static void main(String[] args){
        Solution solution = new Q0036ValidSudoku().new Solution();
    }
    //leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public boolean isValidSudoku(char[][] board) {
        if (board == null || board.length != 9 || board[0].length != 9) return false;
        int[][] rowCount = new int[9][9];
        int[][] colCount = new int[9][9];
        // 3*3子区域内的数字的个数统计，9 * 9 划分为 3* 3 个子区域
        int[][][] subsetCount = new int[3][3][9];
        int val;
        for (int i = 0; i < 9; i++) {
            for (int j = 0; j < 9; j++) {
                if (board[i][j] != '.') {
                    // 注意要 -1， 将1-9 映射为0-8 否则9时会数组越界
                    val = board[i][j] - '0' - 1;
                    rowCount[i][val]++;
                    colCount[j][val]++;
                    // i / 3  划分子区域 0-2 左  3-5 中 6-8 右, j / 3同理
                    subsetCount[i / 3][j / 3][val]++;
                // 不需要再在外部遍历一遍，只需要看看加完只出现一次就行
                if (rowCount[i][val] > 1 || colCount[j][val] > 1 || subsetCount[i / 3][j / 3][val] > 1)
                    return false;
                }
            }
        }
        return true;
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}